HONOLULU -- Honolulu Zoo officials are investigating how one of its tigers escaped from an exhibit on Thursday morning for a brief time.

The tiger escape happened before the zoo opened to the public and no one was injured in the incident, officials said.

Berani, 8, is the zoo's only male tiger. He slipped out of his enclosure at about 8:15 a.m. when a zookeeper had gone in to clean the exhibit area, officials said.

"It appears the zookeeper did not do what was normal protocol -- lock one door, go through and lock another door before going on to his other tasks," Honolulu Enterprise Services Director Sidney Quintal said.

Berani got out of the new tiger exhibit that was completed in November through two gates in the holding area which were left open. The tiger was free to escape when he walked across an open area of the zoo.

He walked past a zoo volunteer and back into another enclosed holding area. The zoo volunteer then closed the door behind him and radioed an emergency call, according to officials.

"In this case, we were on scene in minutes when he was in his holding area. We would have tranquilized him. Had he decided to go somewhere else, we would probably have to put him down, and we were prepared to do that," Quintal said.

Berani was raised by humans. Officials described him as the most docile of the three Sumatran tigers at the Honolulu Zoo.

Zoo officials said they believe the tiger may have been looking for his partner Chrissie.

The Honolulu Zoo recently re-examined its safety procedures following a tiger mauling at the San Francisco Zoo on Christmas Day and declared the zoo in good shape.

The entire incident on Thursday was over in less than half an hour, officials said.

However, Quintal said there is no excuse for what happened and took full responsibility for the incident.

"We're doing everything we can to correct this, and I can assure you we're making every effort to follow protocol," he said.

The zoo opened as scheduled at 9 a.m.

Officials said they are considering whether to enclose the two holding areas behind another gate to avoid such an incident from happening again.

An investigation is underway and another meeting with zoo staff is scheduled for Friday morning.